I am assuming you have a 8p? If so this could help you answer your questions:
1. The answer to this is yes all the trim on the tailgate needs to be removed as you cant just remove the top section.
2. The rubber tube with the wires in connecting the back of the car to the tailgate, is on both the left and right sides of the car, I used the left as this seamed to have more space.
3. Lots of dry lube (PTFE Spray) and nimble fingers!! and I highly recommend getting yourself a device called a cable tongue to feed the wires through the roof liner as this took about a minute with this tool and was super easy!!
Thanks for the info.
In the end, for the time being, I decided not to go into the tail gate and fed the cable along the rear roof trim.
This allowed me to stick the rear camera to the underside of the trim.
This allows the tailgate to be opened and still have the camera facing out of the back of the car. (need to lower the shelf)
Will post a pic to show what I mean.
Decided to buy the Thinkware F800 Pro.
Very clear and hardly noticeable, especially from the rear.
Thanks